There is no universally correct layouting. I for one absolutely detest epub versions of scientific books. Even if they are the official variant and not a generated one from some other format that understandably sucks, diagrams will be all around and I have to go back and forth and lose context. PDFs for all their shortcomings are a godsend and they do their single job perfectly. I much rather zoom in on my phone to a paragraph than look at a badly placed diagram taking up half a page in an unrelated context.